Accurate and reliable delivery of water has, and continues to be, a critical function for irrigating crops, land application of waste water, and environmental control. Since water and electricity are limited resources, efficient methods of ensuring their delivery to the right place and at the right time continue to attract the attention of inventors and designers.
Irrigation controllers or timers have been available for decades, and are a cost-effective component for controlling an irrigation system. There are a number of commercially available, stand-alone irrigation timers that enable a user to preset an irrigation time schedule. These stand-alone irrigation timers execute a schedule, and provide enough power to actuate a latching solenoid thereby providing control for an irrigation valve according to the preset schedule. There are many instances where a plurality of stand-alone irrigation timers are used in a system, and where they are individually programmed to act in concert with one another to satisfy specific requirements of the system.
There are some problems with this approach however. For example, state-of-the-art systems rely on quartz crystal timing, which provides a reasonable level of accuracy for a short period of time; but over time, the clocks in each of these stand-alone irrigation timers slowly drift apart so that they no longer act in concert. This drift leads to unintended operation, and can cause many problems in an irrigation system.
In addition, each individual irrigation timer must be configured or programmed using either an on-board user interface or a dedicated programming fixture increasing the amount of time needed to maintain the system.
The advent of wireless technology promises to provide many opportunities to solve these challenges. For example, dedicated wireless networks managed by a central controller send specific instructions to valves scattered over a wide area. In these systems, the central controller provides a central clock, or system heartbeat, that ensures valves work in concert, even over a long period of time. In this case, the programming for all the valves is centralized at the controller or other remote device that communicates with the controller. In addition, data from the individual valves can be transferred back to the main controller via the wireless link. These advantages overcome many of the problems of the stand-alone timers.
While compelling in many applications, the dedicated wireless network does have its challenges. For example, because of its complexity, it is often higher in cost and energy usage. Additionally, in order for the wireless network to maintain its efficiency, regular messages must be sent by the central controller to keep the network synchronized to maintain its low power state. These regular messages place a power consumption burden upon the central controller making it a larger consumer of energy. If power is interrupted to the central controller, the individual wireless nodes are prone to consume more power, and can run short of energy reserves. To conserve power, wireless nodes are often configured to enter extended sleep periods to preserve their source of power. Bringing these wireless nodes that have entered extended sleep periods back on-line can introduce unacceptable amounts of system latency in some applications. In addition, sending regular synchronization messages adds to network congestion, which could become an increasing problem in the future as more and more wireless networks are deployed, as each system clamors for an increasingly crowded portion of the radio frequency spectrum.
In addition, there are situations where it is difficult to provide reliable wireless signal coverage over a diverse geographic area which is required to maintain synchronization of a wide area wireless system. In order to be successful, such a wide area system must be custom engineered to account for the spatial and geographical constraints. This custom engineering step can significantly increase the cost and complexity of a system limiting its availability for some users.
These and other challenges highlight the need for a new type of irrigation controller and system that provides a low cost, low power, synchronized irrigation control system that can be easily configured and operate using a minimal amount of the radio frequency spectrum. This is the subject of the present patent application.